Note: Descriptions are shown in the official language in which they were submitted.
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SYSTEM FOR SPATIALLY MONITORING A BOREHOLE IN REAL-TIME
Field of the invention
The present invention relates to monitoring systems, for example to monitoring
systems for
monitoring boreholes in connection with oil and/or gas exploration and/or
extraction.
Moreover, the present invention is concerned with methods of monitoring
boreholes in
connection with oil and/or gas exploration and/or extraction. Furthermore, the
present
invention also relates to software products for use in implementing these
aforesaid methods.
Background of the invention
Referring to Figure 1, a borehole indicated generally by 10 is formed in a
region of ground 20
during gas and/or oil exploration. In an event that deposits of oil and/or gas
are found
substantially at an end of the borehole 10, the borehole 10 provides a route
by which the oil
and/or gas deposits can be subsequently extracted. The borehole 10 is often
several
kilometres in depth and filled with liquid, for example:
(a) with drilling mud when executing boring operations during oil and/or gas
exploration;
and
(b) with a multiphase mixture of oil, water and sand particles during
subsequent oil
extraction, namely during production.
In such circumstances, a relatively elevated pressure is often encountered at
the end of the
borehole 10, for example in an order approaching 1000 Bar. Moreover, on
account of
geothermal heating in lower strata of the region of ground 20, an ambient
temperature within
the borehole 10 is susceptible to approaching 150 C for more. Furthermore,
the region of
ground 20 is potentially porous and susceptible to fragmenting into quantities
of gravel and
similar types of sand particles.
In order to successfully drill the borehole 10, it is conventional practice to
line the borehole 10
along at least part of its depth with one or more liner tubes 30a, 30b, 30c,
30d. The liner
tubes 30a to 30d are operable, for example, to prevent water and other
contaminants
penetrating into the borehole 10 at upper regions of the ground 20. Moreover,
the liner tubes
30a, 30b, 30c, 30d are also operable to reduce leakage of oil and/or gas from
the borehole
10. For reasons of economy, the borehole 10 is drilled to have a diameter
sufficient for
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accommodating drilling and/or extraction apparatus 50 as well as providing for
gas and/or oil
extraction; the borehole 10 is not made to be unnecessarily large because
drilling time to
form the borehole 10 and associated costs would thereby be unnecessarily
increased. In
practice, the liner tube 30a is conveniently in an order of 200 mm in
diameter.
Many practical problems are often encountered when drilling the borehole 10;
moreover,
subsequent problems can arise when extracting oil and/or gas via the borehole
10. An
example of such problems is that the liner tube 30a develops one or more
leakage holes.
The one or more leakage holes are susceptible to enabling water and sand
present in the
region of ground 20 to penetrate into a central region of the liner tube 30a;
alternatively, the
one or more leakage holes are susceptible to resulting in a loss for oil
and/or gas from the
liner tube 30a into the ground 20, thereby reducing yield of oil and/or gas
from the borehole
10. Moreover, the liner tube 30a itself is potentially susceptible to becoming
obstructed with
deposits transported up the liner tube 30a, for example sand/oil/tar deposits.
Furthermore, a
flow of liquid and/or gas in an external region between the liner tube 30a and
the ground 20
is also susceptible to occurring which can result in potential pollution,
combustion risk and/or
a loss of pressure within the borehole 10; maintaining a high pressure in the
borehole 10 is,
for example, desirable for achieving an enhanced rate of oil and/or gas
delivery from the
borehole 10. When aforementioned one or more leakage holes and/or obstructions
occur
many kilometres underground, it is often very difficult to know at an above-
ground region 40
what precisely is happening in the ground 20 in respect of the borehole 10. In
view of the
borehole 10 potentially costing many millions of dollars (US dollars) to drill
and prepare for
subsequent oil and/or gas extraction, reliable and efficient detection of
defects arising in the
borehole 10 is of considerable commercial importance. However, physical
conditions within
the borehole 10, for example in lower regions thereof, are very hostile on
account of abrasive
particles present, high ambient temperatures in an order of 150 C or more,
high pressure
approaching 1000 Bar and corrosive and/or penetrative fluids present in the
borehole 10.
Various types of down-borehole tools are known, for example for measuring
multiphase fluid
composition within boreholes. Referring to Figure 2, certain implementations
of these tools
each comprise a probe assembly 100 operatively inserted into the borehole 10
to be
monitored, a data processing arrangement 110 in the above-ground region 40,
and a flexible
communication link 120 mutually coupling together the data processing
arrangement 110
and the probe assembly 100. In operation, the probe assembly 100 senses one or
more
parameters within the borehole 10, for example temperature and/or pressure
therein, using
one or more sensors to generate one or more sensor signals which are then
communicated
via the communication link 120 to the data processing arrangement 110. At the
data
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processing arrangement 110, the one or more sensor signals are at least one
of: displayed
on a display 130 in real-time, recorded in a data memory or data base 140 for
subsequent
analysis. Implementations of the tools, for example as illustrated in Figure
2, optionally
enable real-time monitoring of boreholes to be achieved. A sliding fluid seal
(not shown in
Figure 2) is formed at the top of borehole 10 around a cable implementing the
communication link 120 so as to seal the borehole 10 in an event that the
borehole 10 is
operating under excess pressure, for example as a result the borehole 10
intercepting a gas
deposit in the ground region 20.
Alternatively, as illustrated in Figure 3, other implementations of these
tools each comprise
the probe assembly 100 which additionally includes a semiconductor data memory
150
locally therein for recording signals generated by one or more sensors of the
probe assembly
100 in a first step S1 when the probe assembly 100 is employed to characterize
the borehole
10. In such an implementation, the probe assembly 100 is operable to function
as an
autonomous apparatus which is moved substantially blindly within a borehole 10
to collect
data therefrom. In a step S2, the probe assembly 100 is then subsequently
extracted from
the borehole 10 to the above-ground region 40, whereat the probe assembly 100
is coupled
to its associated data processing arrangement 110 for downloading monitoring
data thereto,
as denoted by 160, namely from the data memory 150 of the probe assembly 100
to the data
processing arrangement 110.
A technical problem is encountered when the probe assembly 100 in Figure 2 is
employed to
spatially inspect, for example by employing one or more optical cameras, an
inside of a
borehole 10 on account of a considerable amount of corresponding data which is
generated.
Measurements such as one or more temperatures within the borehole 10, one or
more
pressures within the borehole 10, and phase composition of fluid within the
borehole 10
generally generate significantly less corresponding amounts of data in
comparison to
executing three-dimensional spatial inspection, for example 360 two-
dimensional imaging
and imaging resulting in perspective images of an inside of the borehole 10
being generated.
In consequence, when spatial inspection is to be performed, severe technical
demands are
placed upon communication performance of the aforesaid communication link 120
in respect
of data bandwidth, or upon data memory capacity which must be provided
robustly within the
probe assembly 100 when operated in an autonomous manner.
It is thus desirable to be able to spatially inspect, in real-time, an inside
of a borehole by
using a probe assembly. On detection of a defect such as a leakage hole or
obstruction, it is
desirable for the probe assembly to be maintained in a locality of the defect
for a longer
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period to sample an enhanced amount of data, thereby enabling the defect to be
identified
and characterized to a greater degree of certainty. By identifying and
characterizing one or
more defects to a greater degree of certainty, repair or mitigation of the one
or more defects
are susceptible to being implemented in a more efficient and selective manner.
A technical problem which the present invention therefore addresses is at
least partially
resolving conflicting constraints of, firstly, real-time monitoring of a
borehole and, secondly,
providing spatial inspection of the borehole which have hitherto seemed
impossible to
adequately resolve.
Summary of the invention
An object of the present invention is to provide an improved monitoring system
which is
operable to enable real-time monitoring of boreholes whilst also enabling
spatial inspection of
boreholes to be achieved.
According to a first aspect of the invention, there is provided a monitoring
system as claimed
in appended claim 1: there is provided a monitoring system for monitoring
within a borehole,
the system comprising a probe assembly operable to be moved within the
borehole for
sensing one or more physical parameters therein, a data processing arrangement
being
located outside the borehole, and a data communication link operable to convey
sensor data
indicative of the one or more physical parameters from the probe assembly to
the data
processing arrangement for subsequent processing and display and/or recording
in data
memory,
characterized in that
(a) the probe assembly includes one or more sensors for spatially monitoring
within the
borehole and generating corresponding sensor signals;
(b) the probe assembly includes a digital signal processor for executing
preliminary
processing of the sensor signals to generate corresponding intermediately
processed
signals for communication via the data communication link to the data
processing
arrangement; and
(c) the data processing arrangement is operable to receive the intermediately
processed
signals and to perform further processing on the intermediately processed
signals to
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generate output data for presentation and/or for recording in a data memory
arrangement.
The invention is of advantage in that preliminary processing executed within
the digital signal
processor is capable of reducing a quantity of measurement data to be
communicated,
thereby rendering possible real-time spatial monitoring of the borehole.
Thus, beneficially, the system is operable to generate the output data for
presentation in real-
time when the probe assembly is moved within the borehole.
Optionally, the system is implemented to be operable in at least one of first
and second
modes, wherein:
(a) the first mode results in the system passively sensing noise sources
present in the
borehole generating radiation for sensing at the one or more sensors; and
(b) the second mode results in the system actively emitting radiation into the
borehole
and receiving at the one or more sensors corresponding reflected radiation
from a
region in and/or around the borehole for generating the sensor signals.
The first mode is of benefit in that it enables sources of noise, for example
leakage holes,
failed seals, cracks and other types of defect through which fluids are
capable of flowing and
generating acoustic noise, to be detected.
More optionally, the system is operable to be dynamically reconfigurable
between the first
and second modes when the probe assembly is being moved in operation within
the
borehole. Such a feature to be able to dynamic reconfigure the system enables
the system
to detect in real-time a greater range of types of features and defects.
However, the system
is optionally adapted for operating specifically solely in the first mode or
in the second mode.
Optionally, the system is operable to communicate data bi-directionally
between the data
processing arrangement and the probe assembly, wherein the digital signal
processor of the
probe assembly is operable to be reconfigured between a first function of
generally sensing
around in a region of the borehole in a vicinity of the probe assembly, and a
second function
of specific sensing in a sub-region of the region of the borehole in a
vicinity of the probe
assembly. Bi-directional communication enables the probe assembly to be
reconfigured to
occasionally concentrating on sensing certain sub-regions of the borehole of
special interest,
thereby using finite communication bandwidth provided by the communication
link in an
efficient manner.
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Optionally, the system is implemented such that the one or more sensors are
implemented
as one or more ultrasonic transducer arrays disposed at one or more positions
on the probe
assembly including:
(a) as an array at a bottom surface of the probe assembly facing down the
borehole
when the probe assembly in inserted into the borehole in operation;
(b) one or more ring formations at one or more ends of the probe assembly, or
radially
around an radial side wall of the probe assembly; and
(c) in one or more rows or one or more spiral formations around a peripheral
surface of
the probe assembly in a substantially longitudinal direction along the probe
assembly.
Optionally, the system is operable to process the sensor signals and compare
the processed
signals with one or more signal templates for automatically detecting features
present in the
borehole which are encountered in operation by the probe assembly. Such
comparison is
optionally based upon correlation and/or neural network analysis techniques.
Optionally, the system is implemented such that the data communication link
comprises one
or more twisted-wire pairs including plastics material insulation and copper
electrical
conductors embedded within the plastics material, the data communication link
being clad by
cladding susceptible to bearing a weight of the probe assembly when the
assembly is moved
in operation within the borehole. Use of twisted pairs is of benefit in
providing a reliable and
stable line impedance for electrical signals and thereby substantially
avoiding end reflections
of electrical signals when appropriately-matched line drivers and receivers
are employed,
whilst providing a mechanically robust implementation when the probe assembly
is
manoeuvred in the borehole.
Optionally, the system is implemented such that the data communication link
comprises one
or more twisted-wire pairs including plastics material insulation and copper
electric
conductors embedded within the plastics material, the data communication link
being
provided with an associated mechanical element susceptible to bearing a weight
of the probe
assembly when the assembly is moved in operation within the borehole.
Optionally, the monitoring system is implemented such that the data processing
arrangement
is located in operation remotely from the probe assembly, the data processing
arrangement
providing an interface for one or more users to control in real-time operation
of the probe
assembly, and for generating graphical images for presenting on one or more
displays to the
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one or more users, the graphical images being representative of spatial
features present
within and/or around the borehole in a vicinity of the probe assembly.
According to a second aspect of the invention, there is provided a method of
monitoring
within a borehole as claimed in appended claim 11: there is provided a method
of monitoring
within a borehole by using a monitoring system, the system comprising a probe
assembly
operable to be moved within the borehole for sensing one or more physical
parameters
therein, a data processing arrangement located outside the borehole, and a
data
communication link operable to convey sensor data indicative of the one or
more physical
parameters from the probe assembly to the data processing arrangement for
subsequent
processing and display and/or recording in data memory,
characterized in that the method includes steps of:
(a) spatially monitoring using one or more sensors of the probe assembly
within the
borehole and generating corresponding sensor signals;
(b) using a digital signal processor included in the probe assembly, executing
preliminary
processing of the sensor signals for generating corresponding intermediately
processed signals;
(c) communicating via the data communication link the intermediately processed
signals
to the data processing arrangement; and
(d) receiving the intermediately processed signals at the data processing
arrangement
for performing further processing on the intermediately processed signals for
generating output data for presentation and/or for recording in a data memory
arrangement.
Optionally, the method includes a further step of:
(e) generating using the system the output data for presentation in real-time
when the
probe assembly is moved within the borehole.
Optionally, the method is implemented such that the monitoring system is
operable in at least
one of first and second modes, wherein:
(a) the first mode results in the system passively sensing noise sources
present in the
borehole generating radiation for sensing at the one or more sensors; and
(b) the second mode results in the system actively emitting radiation into the
borehole
and receiving at the one or more sensors corresponding reflected radiation
from a
region in and/or around the borehole for generating the sensor signals.
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More optionally, the method includes a further step of dynamically
reconfiguring the system
between the first and second modes when the probe assembly is being moved in
operation
within the borehole. Such dynamic reconfiguring enables more diverse types of
features to
be monitored substantially simultaneously using the system in real-time.
Optionally, the method includes a step of:
(f) communicating data bi-directionally between the data processing
arrangement and
the probe assembly, wherein the digital signal processor of the probe assembly
is
operable to being reconfigured between a first function of generally sensing
around in
a region of the borehole in a vicinity of the probe assembly, and a second
function of
specific sensing in a sub-region of the region of the borehole in a vicinity
of the probe
assembly.
Optionally, when implementing the method, the one or more sensors are
implemented as
one or more ultrasonic transducer arrays disposed at one or more positions on
the probe
assembly including:
(a) as an array at a bottom surface of the probe assembly facing down the
borehole
when the probe assembly in inserted into the borehole in operation;
(b) one or more ring formations at one or more ends of the probe assembly, or
radially
around an radial side wall of the probe assembly;
(c) in one or more rows or one or more spiral formations around a peripheral
surface of
the probe assembly in a substantially longitudinal direction along the probe
assembly.
Optionally, the method includes a further step of:
(g) processing the sensor signals to generate corresponding processed signals;
and then
(h) comparing the processed signals with one or more signal templates for
automatically
detecting features present in the borehole which are encountered in operation
by the
probe assembly.
Optionally, when employing the method, the data communication link is
beneficially
implemented using one or more twisted-wire pairs including plastics material
insulation and
copper electric conductors embedded within the plastics material, the data
communication
link being clad by cladding susceptible to bearing a weight of the probe
assembly when the
assembly is moved in operation within the borehole. Such an implementation of
the data
communication link is susceptible to providing a suitable compromise between
data
communication rate, robustness and acceptable manufacturing cost, especially
bearing in
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mind that the communication link and its associated cladding is potentially
many kilometres
long and has to be able to bear its own weight.
Optionally, when employing the method, the data communication link is
beneficially
implemented using one or more twisted-wire pairs including plastics material
insulation and
copper electric conductors embedded within the plastics material, the data
communication
link being provided with a mechanical element susceptible to bearing a weight
of the probe
assembly when the assembly is moved in operation within the borehole.
Optionally, the method includes a step of:
(i) ` locating the data processing arrangement in operation remotely from the
probe
assembly, the data processing arrangement providing an interface for one or
more
users to control in real-time operation of the probe assembly, and for
generating
graphical images for presentation on one or more displays to the one or more
users,
the graphical images being representative of spatial features present within
and/or
around the borehole in a vicinity of the probe assembly.
According to a third aspect of the invention, there is provided a computer
software product
recorded on a data carrier, the computer software product being executable on
computing
hardware for implementing a method pursuant to the second aspect of the
invention.
According to a fourth aspect of the invention, there is provided a probe
assembly for
monitoring in a borehole, the probe assembly being adapted for use in the
system pursuant
to the first aspect of the invention.
Features of the invention are susceptible to being combined in any combination
without
departing from the scope of the invention as defined by the appended claims.
Description of the diagrams
Embodiments of the present invention will now be described, by way of example
only, with
reference to the following diagrams wherein:
Figure 1 is an illustration of a borehole furnished with a liner tube
arrangement;
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Figure 2 is a schematic illustration of a down-borehole probe arrangement for
sensing
physical parameters within a borehole and generating corresponding signals for
communicating in real-time to a data processing arrangement remote from the
borehole;
Figure 3 is a schematic illustration of a down-borehole probe arrangement for
sensing
physical parameters within a borehole and generating corresponding signals for
data-logging locally within a probe assembly, for subsequent down-loading to a
data processing arrangement when the probe assembly has been extracted
from the borehole;
Figure 4 is a schematic illustration of a monitoring system pursuant to the
present
invention for monitoring down boreholes;
Figure 5 is a more detailed illustration of component parts of the system in
Figure 4, the
components including a transducer array for receiving ultrasonic radiation
from
boreholes, and optionally for also interrogating such boreholes;
Figure 6 is an illustration of polar sensing angles of the transducer array of
Figure 5;
Figures 7a and 7b are illustrations of signals present in the system of Figure
4 when in
operation;
Figure 8 is a flow diagram of signal processing operations executed within the
system of
Figure 4; and
Figure 9 is an illustration of a probe assembly of the system of Figure 4
providing
examples of configurations of transducer array which are optionally included
in
the probe assembly.
Description of embodiments of the invention
In overview, embodiments of the present invention include principal features
akin to Figure 2,
namely:
(a) a probe assembly 100 for spatially sensing within a borehole 10;
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(b) a communication link 120 whose associated cladding or mechanical
structural core is
operable to mechanically support the probe assembly 100 when deployed within
the
borehole 10, and whose signal guiding components are operable to convey
signals
transmitted from the probe assembly 100, and to convey control signals to the
probe
assembly 100;
(c) a data processing arrangement 110 coupled via the communication link 120
to the
probe assembly 100, the data processing arrangement 110 being operable to
receive
signals from the probe assembly 100 and to send instruction signals to the
probe
assembly 100.
The probe assembly 100, the communication link 120 and the data processing
arrangement
110 constitute a system as denoted by 300 in Figure 4; the system 300
constitutes an
embodiment of the present invention.
The system 300 is distinguished from subject matter presented and described in
respect of
Figure 2 in that:
(a) the probe assembly 100 includes a transducer array 320 comprising one or
more
sensors coupled via a digital signal processor (DSP) 310 and then via the
communication link 120 to the data processing arrangement 110; and
(b) the data processing arrangement 110 includes a data processor 330 which is
operable to receive data from the probe assembly 100 via the communication
link
120; the data processor 330 is also operable to send control commands via the
communication link 120 to reconfigure the digital signal processor (DSP) 330,
for
example in response to one or more signals generated in operation by the
transducer
array 320.
The system 300 is optionally susceptible to operating in at least one of a
first passive mode
and a second active mode.
In the first passive mode, one or more physical signals 350 that are generated
in an
environment of the borehole 10 propagate within the borehole 10 and are
eventually received
by the transducer array 320. The transducer array 320 generates one or more
corresponding electrical signals 360 which are conveyed to the digital signal
processor
(DSP) 310. Thereafter, the digital signal processor 310 performs primary
processing of the
one or more electrical signals 360 to generate corresponding intermediate
processed signals
370 which are communicated via the communication link 120 to the data
processor 330. The
data processor 330 then performs secondary processing on the intermediate
processed
signals 370 to generate corresponding output data. Moreover, the data
processor 330 is
optionally operable to store at least part of the intermediate processed
signals 370 in the
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data memory 140. Moreover, the data processor 330 is optionally operable to
store at least
part of the output data in the data memory 140. Moreover, the data processor
330 is
operable to present the output data on the display 130.
In the second active mode, the data processor 330 is operable to send control
signals 380 to
the digital signal processor (DSP) 310 to drive the transducer array 320 with
one or more
drive signals 390 to cause the transducer array 320 to emit radiation 400 into
the borehole
10. Optionally, the emitted radiation 400 is pulsed radiation comprising
pulses punctuated by
quiet periods; portions of the radiation 400 reflected from structures within
and in near
proximity to the borehole 10 are received back at the transducer array 320 as
the one or
more physical signals 350 to generate the corresponding one or more electrical
signals 360
which are subsequently processed in the digital signal processor 310 to
subsequently
generate the intermediate processed signals 370. The data processor 330 then
performs
secondary processing of the intermediate processed signals 370 to generate
corresponding
output data. Moreover, the data processor 330 is optionally operable to store
at least part of
the intermediate processed signals 370 in the data memory 140. Moreover, the
data
processor 330 is optionally operable to store at least part of the output data
in the data
memory 140. Moreover, the data processor 330 is operable to present the output
data on
the display 130.
The system 300 is optionally designed to be able to switch dynamically between
the
aforementioned first passive mode and second active mode. Alternatively, the
system 300 is
optionally designed to function only in the first passive mode, for example
optimized to
function in the first passive mode. Yet alternatively, the system 300 is
optionally designed to
function only in the second active mode, for example optimized to function in
the second
active mode.
It will be appreciated from the foregoing that the system 300 is operable to
distribute data
processing activities between the digital signal processor 310 and the data
processor 330.
Such a distribution of data processing activities is of benefit in that data
reduction within the
probe assembly 100 is feasible to achieve so that available bandwidth of the
communication
link 120 is not occupied by data which bears relatively irrelevant
information. By such data
reduction, for example achieved by various data compression techniques which
will be
described in more detail later, it becomes feasible to provide real-time
images of the
0
borehole 10 on the display 130 at a sampling rate which is practical for the
probe assembly
100 to be moved at an acceptably fast velocity up or down the borehole 10 for
investigating
defects therein or in a vicinity thereof. When the borehole 10 is many
kilometres in length,
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an inspection rate when using the system 300 beneficially corresponds to
several metres per
second along the borehole 10. It is desirable that the system 300 is operable
to perform
metrology on the borehole 10 within a time period of I to 20 hours when the
borehole 10 has
a length in an order of kilometres. When the borehole 10 is implemented for
gas extraction,
the system 300 is susceptible to being used concurrently with gas extraction
being
performed.
The system 300 has been described in overview in the foregoing. However,
before
describing component parts of the system 300 in greater detail, other issues
regarding the
probe assembly 100 will next be elucidated. The borehole 10 is often at a
pressure P which,
in certain circumstances, can approach 1000 Bar. For example, the borehole 10
can often
be many kilometres deep and filled with water, or with an abrasive multiphase
mixture
including oil, water and rock particles. When the probe assembly 100 is
lowered into the
borehole 10 filled with liquid to a depth of a kilometre or more, the pressure
P acting upon the
probe assembly 100 is potentially enormous. In such circumstances, a leakage
hole in the
liner tube 30a with many Bar differential pressure between a first region
outside the liner tube
30a to a second region inside the liner tube 30a potentially results in a
considerable flow of
fluid between the first and second regions causing turbulent generation of
acoustic radiation
from a vicinity of the leakage hole. It is also feasible in certain situations
that the borehole 10
is filled with gas at a high pressure approaching 1000 Bar on account of the
borehole 10
intercepting a gas reservoir. Such high pressures in the borehole 10 risk
forcing gas or liquid
to ingress into an inside region of the probe assembly 100 and can also force
gas into a
polymeric material from which the cladding 200 is fabricated. For example, if
the cladding is
fabricated from polymeric material and is suddenly depressurized from a high
pressure of
1000 Bar pressure to nominal atmospheric pressure of 1 Bar (760 mm Hg), gas
forced by
such a high pressure to earlier ingress into interstitial spaces within the
polymeric material is
susceptible to cause the polymeric material to expand to form a foam-like
material with
microvoids therein, potentially resulting in permanent damage to the polymeric
material.
Optionally, as illustrated in Figure 1, the inner liner tube 30a includes a
seal around a top
region thereof as illustrated in Figure 1 when the borehole 10 is required in
operation to
exhibit an elevated pressure relative to ambient atmospheric pressure of
nominally
substantially I Bar (760 mm Hg). The seal is beneficially adapted to be
capable of sealing
around the cladding 200, for example in a sliding manner, when the probe
assembly 100 is
deployed within the borehole 10. Although a use of a polymeric material to
form the cladding
200 to clad the communication link 120 is virtually unavoidable, a casing of
the probe
assembly 100 is beneficially fabricated from a robust material which is
resistant to abrasion
and corrosion, for example fabricated from machined solid stainless steel
material or
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seamless stainless steel tubing. Alternatively, or additionally, at least a
portion of the probe
assembly 100 can be fabricated from more exotic materials, for example
advanced rigid
polymer materials, silicon nitride material, and/or ceramic material for
example.
The transducer array 320 is beneficially implemented as an array of one or
more piezo-
electric elements, for example fabricated from lead zirconate titanate (PZT)
or similar
strongly piezo-electric material. In operation, the transducer array 320 is
susceptible to being
excited by the one or more drive signals 390 applied thereto to generate the
radiation 400 as
ultrasonic radiation, and also susceptible to receive the radiation 350 as
reflected ultrasonic
radiation for generating aforesaid one or more electrical signals 360. Piezo
electric material
of the transducer array 320 is optionally directly in physical contact with
fluid present within
the borehole 10 in order to obtain most efficient coupling of ultrasonic
radiation.
Alternatively, the transducer 320 is operable to communicate with the interior
region of the
borehole 10 via one or more interfacing windows.
On account of the borehole 10 being potentially heated up to a temperature T
approaching
150 C by geothermal energy in rock formations surrounding the borehole 10,
there is a
potentially severe limitation regarding power dissipation which can occur
within the probe
assembly 100 when in operation. When the probe assembly 100 is operating
pursuant to the
aforesaid second active mode, generating the one or more drive signals 390 in
drive
amplifiers is susceptible to resulting in electrical power dissipation within
the probe assembly
100. Moreover, data processing occurring in operation in the digital signal
processor (DSP)
310 is susceptible to causing additional dissipation in both the first passive
mode and in the
second active mode.
Optionally, the digital signal processor (DSP) 310 is provided with one or
more Peltier cooling
elements for optionally cooling the signal processor 310; however, use of the
one or more
Peltier cooling element is susceptible to adding to a total dissipation
occurring within the
probe assembly 100 and is therefore only employed selectively where effective
cooling of the
processor 310 is susceptible to being thereby achieved.
The digital signal processor (DSP) 310 is beneficially implemented using
semiconductor
devices based upon CMOS technology which are not vulnerable to thermal runaway
as a
result of increase in minority-carrier currents therein during operation.
Similarly, the drive
amplifiers employed within the probe assembly 100 to provide the one or more
drive signals
390 are beneficially also based upon MOSFET devices which are capable of
operating at
elevated temperatures approaching 200 C without suffering thermal runaway.
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Alternatively, or additionally to employing the one or more Peltier cooling
elements, the signal
processor 310 is implemented using several integrated circuits to spread power
dissipation
and therefore try to avoid hot-spots wherein a silicon die of an integrated
circuit is at an
elevated temperature relative to its local environment on account of
dissipation occurring
within the die during operation. Optionally, the several integrated circuits
are fabricated as a
hybrid module, for example including a ceramic substrate providing a low
thermal resistance
path to an ambient environment within the probe assembly 100.
On account of the liner tube 30a having an inside diameter in an order of 200
mm, the probe
assembly 100 is manufactured to have a diameter in a range of 100 mm to 180
mm, more
preferably to have a diameter of substantially 150 mm. Moreover, the cladding
200 of the
communication link 120 is optionally required to be strong enough to bear a
weight of the
probe assembly 100 when lowered kilometres down the borehole 10 including a
weight of the
cladding itself; alternatively, or additionally, one or more mechanical
supporting elements, for
example one or more high-tensile steel ropes, are optionally employed to bear
a weight of
the probe assembly 100 when deployed in the borehole 10. If the cladding 200
is relatively
larger in diameter, for example 25 mm or greater in diameter, it becomes too
massive and is
difficult to bend around pulleys of feed hoists above the borehole 10.
Conversely, if the
cladding 200 is relatively small in diameter, for example 4 mm or smaller in
diameter, the
cladding 200 is susceptible to becoming snarled on projections forming in
operation on an
inside-facing surface of the borehole 10 and is potentially unable to reliably
bear its own
weight and also the weight of the probe assembly 100. In practice, with modern
advanced
cladding materials, for example by using one or more of carbon fibres, Kevlar
and advanced
nano-material fibres, it is feasible to provide sufficient robustness for the
cladding 200 when
the cladding has a diameter in a range 5 mm to 15 mm, more preferable a
diameter in a
range of 6 mm to 10 mm, and most preferably a diameter of substantially 8 mm.
In operation, the cladding 200 is susceptible to exhibiting strain when a
stress arising from
weight is applied thereto. Optical fibres are not robust to stretching and can
potentially be
fractured when undergoing even modest longitudinal strain. In consequence, the
communication link 120 is implemented as one or more electrical twisted pairs
of wires.
Optionally, the one or more electrical twisted pairs of wires are included
within one or more
overall electrically-conductive braided screens or similar. The wires each
include plastics
material insulation which is capable of stretching under stress. Moreover,
each wire includes
copper conductors therein; copper is a ductile metal of relatively low weight,
of high electrical
conductivity, of relatively high resistance to oxidative corrosion, and is
less prone to work
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hardening when subjected to repeated bending cycles in comparison to other
metals. At
each end of the communication link 120 is included Ethernet line drivers
matched to a
transmission-line impedance of the one or more twisted-wire pairs of the
communication link
120; data is thereby bi-directionally communicated in operation along the
communication link
120 which is capable of enabling a data flow of several hundred kbytes per
second to be
supported. It is however to be bourn in mind that conventional real-time
streaming of two-
dimensional video images often requires a communication bandwidth in the order
of MHz.
The data processing arrangement 110 is implemented as a configuration of
proprietary
components and is susceptible to being installed: on-land, on a sea-going
vessel, in a
submarine, on an oil exploration platform, or on an air-borne vehicle via an
additional
wireless link. The data processor 330 and the display 130 are beneficially
implemented
using proprietary computing hardware; the data processor 330 beneficially has
a data entry
device, for example a keyboard and a computer tracker-ball mouse, for enabling
one or more
users 450 to control operation of the system 300 in real-time. The data
processor 330 is
coupled in communication with the data memory 140 which is conveniently
implemented by
using at least one of: semiconductor memory, optical data memory, magnetic
data memory.
Operation of the system 300 will now be described in greater detail.
During exploratory drilling activities for gas and/or oil, expensive and
complex equipment is
used under the supervision of experienced technical staff. In consequence,
drilling and lining
the borehole 10 with the liner tubes 30 is an extremely expensive activity,
for example often
costing in a region of a million United States dollars per day. When such high
costs are
encountered, problems occurring within the borehole 10 need to be identified
quickly and
resolved promptly. Even an operation of removing a drill bit and its
associated string from
the borehole 10 is a major undertaking, in some cases corresponding to several
days of
expensive work. When applied to monitor the borehole 10, for example after
removal of a
drill bit and associated drive string therefrom, the system 300 needs to be
highly reliable,
susceptible to being rapidly deployed into the borehole 10, and to provide
flexibility in use by
way of real-time monitor to avoid a need to repeatedly reinsert the probe
assembly 100 into
the borehole 10 when performing metrology thereon and monitoring thereof.
Referring to Figure 5, the transducer array 320 comprises an array of one or
more piezo-
electric transducer elements 460 operable to at least receive ultrasonic
radiation denoted by
the radiation 350 from the borehole 10; there are n transducer elements in the
transducer
array 320, wherein a number n is beneficially in a range of one to several
thousand, more
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preferable a plurality of transducer elements. As elucidated in the foregoing,
the radiation
350 is generated by one or more processes occurring in the borehole 10 when
the system
300 is operating in the first passive mode, and is generated by reflection of
the radiation 400
when the system 300 is operating in the aforesaid second active mode. As
described earlier,
the array of transducer elements 460 optionally ultrasonically communicate via
an interfacing
member 452 which transmits ultrasonic radiation therethrough as well as
protects the
transducer elements 460 from a harsh environment within the borehole 10.
The one or more transducer elements 460 in the transducer array 320 are
operable to
generate signals Si eiOt wherein i is in a range of I to n; the signals S;
correspond to the
electrical signals 360 described earlier. Beneficially, one or more of the
transducer elements
460 are operable to emit and/or receive ultrasonic radiation having a
frequency in a range of
100 kHz to 10 MHz when the system is operating pursuant to the second active
mode, and
more preferably in a range of 500 kHz to 5 MHz. Such a frequency range is of
benefit it that
individual transducer elements are susceptible to being implemented in a
compact manner
and that ultrasound at such frequency has a relatively short wavelength in an
order of 1 mm.
Conversely, one or more of the transducer elements 460 are operable to receive
ultrasonic
radiation having a frequency in a range of a few hundred Hz to several hundred
kHz when
the system 300 is functioning in the first passive mode, depending on which
type of
monitoring is to be performed within the borehole 10. The digital signal
processor 310 is
operable to condition one or more of the signals Si in a manner of a phased
array algorithm
to steer a direction of greatest sensitivity of the transducer array 320. Such
steering is
achieved by performing two principal steps in the digital signal processor
310.
The first step of beam forming involves selectively phase shifting and scaling
the signals Si
under control of various control parameters. Moreover, the first step is
performed in
computing hardware of the digital signal processor 310 operable to execute a
software
product stored on a data carrier, for example the data carrier being a non-
volatile
semiconductor data memory associated with the digital signal processor 310. In
the first
step, the signals S;= are subject to scaling and phase shifting operations as
defined by
Equation 1 (Eq. 1) to generate corresponding intermediate processed signals
Ht:
H1 = ASe'a eCos 01+.; sine E q.1
wherein
j = square route of -1;
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w = angular frequency of signal component of interest;
t= time;
B; = phase shift applied for beam forming purposes;
A; = scaling coefficient for beam forming purposes.
The second step of beam forming selectively summing one or more of the
intermediate
processed signals H; as defined by Equation 2 (Eq. 2) to generate
corresponding signals B,,6
representative of a component of radiation received at the transducer array
320 from a
specific direction as follows:
S
Ba,/j H; Eq.2
wherein
a, 8= angles define the specific direction relative to an orientation of the
transducer array
320 in which the transducer array 320 is preferentially sensitive for
generating the
signal Ba Q; and
r, s = index values defining which intermediate signals H; to be selectively
summed to
generate the signal Ba Q.
The signals H; to be summed optionally do not necessarily need to lie
consecutively in series
of index value i; for example appropriate scaled and phase-shifted signals S;
for i = 1, 10, 12,
15 can be selectively combined to generate the signal Ba Q. The angles a and
,8 are
susceptible to being defined, for example, as illustrated in Figure 6. A
mathematic mapping
relates the angles a,,6 to corresponding phase shift B; and scaling
coefficient A; are denoted
by function G in Equation 3 (Eq. 3):
(B,A) = G(aõ l3) Eq.3
wherein the function G is determined by a geometry and configuration of the
transducer array
320. The function G is optionally pre-computed and stored as a mapping in data
memory, for
example in a form of a look-up table; the look-up table is beneficially stored
in at least one of
the data processing arrangement 110 and the digital signal processor 310.
Alternatively, the
function G can be computed in real-time from parameters in at least one of the
data
processing arrangement 110 and the digital signal processor 310.
The signals Ba,,g are computed using at least Equations 1 and 2 (Eq. 1 and 2)
in real-time
and then communicated from the digital signal processor 310 via the
communication link 120
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to the data processor arrangement 110 for further processing there.
Optionally, for example
under control from the data processing arrangement 110 communicated via the
communication link 120 to the probe assembly 100, the signals Si are
communicated directly
in real-time, namely directly streamed, in a substantially unprocessed state
via the
communication link 120 to the data processing arrangement 110 and a majority
of data
processing then performed in the data processing arrangement 110.
As elucidated in the foregoing, the system 300 is designed to economize on a
way in which
an available bandwidth of the communication link 120 is utilized in operation.
Data flow
reduction is susceptible to being achieved by one or more of following
approaches:
(a) by dynamically instructing the probe assembly 100 only to send the signals
Si or the
signals Ba F corresponding to radially directions defined by Ba Q of special
interest,
thereby avoiding to process and send data for directions which are not of
interest;
(b) by dynamically instructing the digital signal processor 310 only to
process signals
from a subset of the transducers 460, corresponding to a reduction in angular
and
spatial resolution, for example by dynamically adjusting values for limit
indexes r, s;
this saves computing effort and power dissipation within the probe assembly
100;
(c) by dynamically instructing the digital signal processor 310 to send the
signals
corresponding to Ba, p or Si at a reduced resolution, for example by only
sending more
significant bits of data bytes whilst maintaining computational accuracy
within the
digital signal processor 310; and
(d) by performing a fast Fourier transform (FFT) at the digital signal
processor 310 of the
signal 8a,p to generate corresponding Fourier spectrum coefficients Fa,8 and
then by
communicating the spectrum coefficients Fa,6 via the communication link 120 to
the
data processing arrangement 110, namely by adopting a parameterized data
compression process.
Optionally, in approach (d), the digital signal processor 310 is operable to
compare, for
example by a correlation-type technique or using a neural network approach,
the Fourier
spectrum coefficients FIX,6 with templates of frequency spectra of specific
types of known
defects occurring within boreholes, for example leakage holes, obstructions,
cracks and so
forth. In an event of the computer frequency spectrum Fa,,6being sufficiently
similar, within a
threshold limit, to one or more of the frequency spectra of the one or more
templates, a
defect in the borehole 10 is deemed to have been found; in such case of
finding a defect for
the angles a,,8, the digital signal processor 310 is operable to simply send
an identification
that one or more defects have been detected and a nature of the one or more
defects. Such
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an extension of the approach (d) represents considerable data processing in
the probe
assembly 100 but also provides a very high degree of data compression which
potentially
enables, for a given bandwidth available in the communication link 120, the
probe assembly
100 to be advanced at a greater longitudinal velocity along the borehole 10
whilst
simultaneously providing real-time monitoring. In an event that the borehole
10 is mostly free
of defects along its length, such an approach as in (d) results in a
relatively smaller amount
of data exchange along the communication link 120 until a defect is found; in
such an event
that a defect is found, the system 300 is, for example, capable of dynamically
switching from
the approach as in (d) to comprehensive sampling of the signal Bap when the
probe
assembly 100 is in close proximity to the detected defect and whilst the probe
assembly 100
is manoeuvred more slowly relative to the detected defect.
When the system 300 is operated in the first passive mode, a signal Ba,p as
illustrated in
Figure 7a is often obtained. In Figure 7a, there is an absence of any drive
signal Sd, 390
applied to the transducer array 320; such absence is denoted by a horizontal
line in Figure
7a. Noise generated within the borehole 10 is received at the transducer array
320 and
gives rise to a resolved noise-like chaotic signal as illustrated in Figure
7a.
Conversely, when the system 300 is operated in the second active mode, the
transducer
array 320 is driven with the one or more drive signals Sd 390 which are
optionally phase
shifted and amplitude adjusted so that the transducer array 320 emits a beam
of ultrasonic
radiation in a preferred direction. Alternatively, the transducer array 320 is
driven with the
one or more signals Sd 390 to emit ultrasonic radiation more omni-
directionally from the
transducer array 320. The one or more drive signals Sd 390 optionally include
a temporal
sequence of single excitation pulses mutually separated by a time duration At;
such
excitation single pulses approximate to pseudo-Dirac pulses and excite a
natural mode of
resonance of the transducer array 320 such that the radiation 400 is emitted
at a frequency
of this natural mode of resonance. Conversely, when the drive signal Sd 390 is
a periodically
repeated sequence of a burst of pulses 600 as illustrated in Figure 7b, the
frequency of the
radiation 400 is susceptible to being at least partially defined by a pulse
repetition frequency
within the burst of pulses 600.
When operating in the second active mode, the burst of pulses 600 results in
instantaneous
direct signal breakthrough coupling, for example by way of direct
electrostatic and/or
electromagnetic coupling, giving rise to an initial detected pulse 610 which,
optionally, can be
gated out without the digital signal processor 310. A pulse wavefront in the
radiation 400
propagates from the transducer array 320 to an inside facing surface of the
liner tube 30a
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wherefrom a portion of the radiation 400 is reflected and propagates as a
component of the
radiation 350 back to the transducer array 320 to give rise to a reflected
pulse 620 as shown
in Figure 7b in the resolved signal Ba, p. A proportion of the radiation 400
is further coupled
into the liner tube 30a and is reflected from an exterior facing surface of
the liner tube 30a
back through the liner tube 30a and further as another component of the
radiation 350 back
to the transducer array 320 to give rise after resolving to a weaker pulse 630
as shown in
Figure 7b in the resolved signal B, p In an event that an obstruction is
present on an inside
surface of the liner tube 30a, a pulse corresponding to the obstruction will
be observed
before the pulse 620. Moreover, in an event that the liner tube 30a is cracked
or fractured,
reflections forming the pulses 620, 630 will be confused, namely a convoluted
and
attenuated mixture of signal components. A portion of the radiation 400 is
susceptible to
propagating through the liner tube 30a and propagating further into a region,
for example a
cavity, between an external surface of the liner tube 30a and the ground 20;
the region
represents an abrupt spatial acoustic impedance variation and results in a
portion of the
radiation thereat being reflected back to the probe assembly 100. The system
300 is thereby
capable of performing metrology on such a region between the external surface
of the line
tube 30a and the ground 20. Such a region is susceptible, for example, to
providing a path
for leakage of oil and/or gas up the borehole 10 externally to the line tube
30a.
In the first passive mode of operation of the system 300, spectral analysis,
for example
executed using a form of fast Fourier transform, of acoustic radiation
generated by fluid flow
through leakage holes and around an exterior of the liner tube 30a enables
certain
categories of defects to be detected. Conversely, when fluid flow is not
occurring within the
borehole 10, the second active mode of operation enables other types of
defects to be
identified. As elucidated in the foregoing, the system 300 is capable of being
optimized for
operating solely in either the first passive mode or solely in the second
active mode.
Alternatively, the system 300 is capable of being implemented to be able to
function in both
the first passive mode and the second active mode; for example, the system 300
is capable
of being implemented to dynamically switch between the first and second modes
in real-time
when making measurements within the borehole 10.
Optionally, in order to reduce a quantity of data to be communicated via the
communication
link 120 when the system 300 is operating in the second active mode, the
digital signal
processor 310 is optionally configurable from the data processing arrangement
110 to
analyze the signal Ba, p to identify times tp when reflection pulses, for
example the pulse 620,
630, occur after their corresponding excitation burst of pulses 600 or single
excitation pulse,
and to determine their corresponding amplitudes U, and then communicate time
of reflected
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pulse information to and corresponding amplitude U as descriptive parameters
via the
communication link 120 to the data processing arrangement 110, thereby
achieving
potentially considerable data compression in comparison to communicating the
signal B,,6
directly to the data processing arrangement 110; a rate at which the probe
assembly 100 is
capable of being advanced along the borehole is thereby potentially
considerably enhanced
in real-time when data compression is utilized.
Operation of the data processing arrangement 110 will now be further
elucidated. When
data is communicated from the probe assembly 100 via the communication link
120 to the
data processing arrangement 110, the processing arrangement 110 is optionally
operable to
record the received data from the probe assembly 100 as a data log in the data
memory 140.
Such a record enables, for example, subsequent analysis to be performed after
the probe
assembly 100 has been extracted from the borehole 10, for example to perform
noise
reduction operations for increasing a certainty of detection of various types
of defects in the
borehole 10. The data processor 330 is operable to execute one or more
software products
which apply further analysis and conditioning of data received via the
communication link 120
from the probe assembly 100.
In real-time, when the system 300 is functioning in the second mode of
operation, the data
processor 330 presents on the display 130 a local 3-dimensional view of an
interior of the
borehole 10 substantially at a depth z at which the probe assembly 100 is
positioned within
the borehole 10, for example refer to Figures 2, 3 and 5 for a definition of
the depth z; in
Figure 5, increasing depth z is in an upward direction in the drawing. Such
representation on
the display 130 in the second active mode of operation enables the one or more
users 450 to
visually spatially inspect the inside surface of the liner tube 30a in real-
time. Time instances
of receipt, for example, of the reflected pulses 620, 630 at the transducer
array 320 provides
an indication of the spatial location of the inside and outside surfaces of
the liner tube 30a
and also potentially an ultrasonic radiation view of material surrounding an
exterior of the
liner tube 30a.
Alternatively, in the first passive mode of operation of the system 300, there
is provided an
indication of potential defects or ultrasonic noise sources as a function of
the depth z and the
angles a, /3, see Figure 6. A different type of presentation is then
optionally provided on the
display 130 illustrating identified defect and/or noise type as a function of
radial position as
defined by the angles a,,8, and the depth z.
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When the system 300 is configured to function in the second active mode, the
data
processor 330 employs one or more software products which operate to map the
signal Ba a
by a mapping function M to a Cartesian or a polar coordinate data array,
namely w (x, y, z) or
w (a,,8, z), as denoted as a mapping step 700 in Figure 8 and described by
Equation 4 (Eq.
4):
W (x, y, z) = M (B.,,6, z)
w (a, Q, Z) = M (Ba, P z) Eq.4
Values stored in elements w of the data array correspond to strength of
reflected ultrasonic
radiation, namely aforementioned U, as determined from reflection pulse peak
amplitude in
the signal B,,,a.
The signal B,,p, for example as illustrated in Figure 7b, is optionally
communicated to the
data processing arrangement 110 in data-compressed in a parameterized form as
elucidated
earlier. By action of the mapping function M, the data array w thereby has
stored therein a
spatial crude 3-dimensional image of an inside view of the borehole 10 wherein
an array
element w position is equivalent to a corresponding spatial position within
the borehole 10.
Thereafter, in a gradient computation step 710, the data processor 330 is
operable to apply a
gradient-determining function to determine 3-dimensional gradients in element
w signal
amplitude values stored in the data array w (x, y, z) or w ( a,,3, z), namely
to determine
whereat spatial boundaries between features are present in the ultrasonic
image of the
borehole 10 recorded in the data array w. Identification of spatial boundaries
is also known
as "iso-surface extraction" in the technical art of image processing and
involves computation
of partial differentials of the array elements w as provided in Equation 5
(Eq. 5):
aw aw aw aw aw 8w
Eq.5
ax' ay' az or aa,a,3' az
depending upon whether Cartesian or polar coordinate systems are employed.
In a step 720, the one or more software products are then operable to enhance
values in the
data array w, for example by curve fitting techniques, to show more clearly
whereat
continuous boundaries occur in the elements w (x, y, z) or w (a, ,6, z) stored
image data
store in the data memory of the data processor 330. Such curve fitting
operations offer a
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smoothing function so that images presented on the display 130 are not
cluttered with
irrelevant surface texture details, but nevertheless show relevant features
regarding integrity
and operation of the borehole 10. Optionally, a step of smoothing is
alternatively performed
before a step of extracting iso-surfaces is performed.
Thereafter, in a step 730, the data processor 330 is operable to read data
from the element
w of the data array and then write corresponding presentation values, after
geometrical
transformation when necessary, into a memory buffer serving the display 130.
Optionally, in an event that the one or more software products executing on
the data
processor 330 identify when extrapolating one or more boundaries in the image
stored in the
elements w of the data memory to be unclear, the data processor 330 is then
operable in
real-time to instruct, as denoted by 740, the digital signal processor 310 for
specific values of
the angles a,,8 to repeat measurements within the borehole 10 for resolving
such lack of
clarity in the image stored at the data processor 330. Such instruction to the
digital signal
processor 310 optionally includes one or more of:
(a) causing the probe assembly 100 to employ its digital signal processor 310
to
appropriately phase shift and scale pursuant to Equations I and 2 (Eqs. 1 and
2)
more of its electrical signals S; to generate corresponding values of the
signal Bap
thereby having greater directional definition and resolution, the signals Baa
being
subsequently communicated to the data processing arrangement 110 for further
data
processing and subsequent presentation on the display 130;
(b) averaging, namely filtering, over numerous samples of the signal S; to
reduce noise
for a limited range of specified angular sensing directions defined by the
angles a, /3,
and then computing corresponding signals Ba, p for communicating via the
communication link 120 to the data processing arrangement 110 for subsequent
further data processing thereat and thereafter presentation on the display
130;
(c) driving the transducer array 320 in the manner of a phased array so that
more of its
ultrasonic radiation 400 is delivered into a particular direction in which
metrology and
monitoring was previously unclear, acquiring further vales of the signal Si
and
subsequently computing corresponding signals Ba, p for communication to the
data
processing arrangement 110 for further data processing at the data processing
arrangement 110 and thereafter presentation on the display 130; and
(d) acquiring a larger set of measurements over a given defined limited range
of angles
a, 8 so as to map out finer details of a feature present in the borehole 10,
processing
corresponding acquired signals Si to generate corresponding signals Ba, fl,
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communicating the signals Ba R via the communication link 120 to the data
processing
arrangement 110 for further data processing and eventual presentation on the
display
130.
Beneficially, one or more of the users 450 as well as the data processing
steps as illustrated
in Figure 8 are able to invoke a reconfiguration of the probe assembly 100 to
acquire
enhanced information from one or more regions of the borehole 10. After the
enhanced
information is acquired b the system 300, the system 300 is beneficially
operable to revert
back to its previous configuration state to continue monitoring the borehole
10. Thus, during
monitoring operations involving manoeuvring the probe assembly 100 of the
system 300
along the borehole 10, the system 300 is optionally set to perform a method
comprising steps
of:
(a) performing a series of spatially coarse measurements along the borehole 10
whilst
monitoring in real-time for any trace of one or more defects or other unusual
features
in the borehole 10;
(b) detecting one or more potential defects or other unusual features at a
location along
the borehole 10 in real-time;
(c) reconfiguring the probe assembly 100 to perform a selective more detailed
series of
measurements of the one or more defects or other unusual features; and
(d) after executing the more detailed series of measurements in step (c),
resuming the
series of spatially coarse measurements along the borehole 10 as in step (a).
This method is capable of being employed when the system 300 is operating in
its first
passive mode or in its second active mode. Optionally, the system 300 is
beneficially
operable to dynamically switch in real-time between the first and second modes
when
performing the series of spatially coarse measurements along the borehole 10.
It will be appreciated that the system 300 is operable to provide 2-D images
of an inside of
the liner tube 30a, and also information of a region between an outside of the
liner tube 30a
and the ground 20, for example an existence of voids or cavities, Moreover,
the system 300
is capable of generating 3-D views, for example perspective views on planar
screens such as
liquid crystal pixel display screens, which are most readily interpreted by
human visual
viewing.
It will be appreciated that embodiments of the invention as described in the
foregoing are
susceptible to being modified without departing from the scope of the
invention as defined by
the appended claims.
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Beneficially, the probe assembly 100 is furnished with one or more pressure
sensors for
measuring a pressure P present within the borehole 10 as the probe assembly
100 is
manoeuvred in operation along the borehole 10. In an event that the probe
assembly 100
detects that the pressure P in the borehole 10 becoming excessive, for example
in excess of
500 Bar, the probe assembly 100 is operable to transmit a warning message to
the one or
more users 450.
Beneficially, the probe assembly 100 is furnished with a temperature sensor
for measuring
an operating temperature T within the probe assembly 100. In an event that the
operating
temperature T exceeds a predefined threshold temperature Th, the probe
assembly 100 is
operable to send a request to the data processing arrangement 110 to enable
the probe
assembly 100 to assume intermittent operation, wherein the digital signal
processor 310 is
permitted intermittently to enter a hibernating low-power state in order to
provide the digital
signal processor 310 with an opportunity to cool slightly by reducing
electrical power
dissipation therein. When in the hibernating state, advance of the probe
assembly 100 along
the borehole 10 is optionally temporarily halted. Optionally, such
intermittent operation of the
signal processor 310 is progressively more adopted as the operating
temperature T exceeds
above the threshold temperature Th. Beneficially, the data processing
arrangement 110 is
susceptible to being instructed to temporarily assume a hibernating state
during which its
power dissipation is reduced in comparison to its normal non-hibernating
operation.
The transducer array 320 is described briefly in the foregoing. In Figure 9,
there is shown
an illustration of the probe assembly 100, wherein the array 320 is
susceptible to being
implemented in various configurations, for example at least one of:
(a) a rectangular matrix 800 of mutually perpendicular rows and columns of
individual
transducer elements, for example cut from a single slab of polarized piezo-
electric
material, for example by using a fine diamond saw; peripheral edges of the
matrix
800 are optionally straight or curved; the rectangular matrix is beneficially
mounted at
a bottom surface of the probe assembly 100 facing down the borehole 10 when
the
probe assembly 100 is in operation;
(b) a series of individual transducer elements arranged in one or more ring
formations
810; the ring formation is beneficially mounted at one or more ends of the
probe
assembly 100, or radially around an radial side wall of the probe assembly
100; and
(c) in one or more rows 830 or a spiral formation 840 around a peripheral
surface of the
probe assembly 100 in a substantially longitudinal direction along the probe
assembly
100.
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Optionally, the probe assembly 100 further includes an electronic compass for
measuring a
direction of the Earth's north and south magnetic poles at the probe assembly
100 in order to
provide a corresponding orientation signal for communicating via the
communication link 120
to the data processing arrangement 110; receipt of such an orientation signal
enables the
data processor 330 to correct for the angle /3 as shown in Figure 6 when the
probe assembly
100 is lowered into the borehole 10 and revolves during its descent into or
during subsequent
extraction from the borehole 10. The probe assembly 100 is thus beneficially
fabricated
from non-ferromagnetic materials, for example non-magnetic stainless steel.
The probe assembly 100 beneficially has an exterior diameter "d" in a range of
100 mm to
180 mm, more beneficially a diameter in a range of 120 mm to 160 mm, and most
beneficially substantially a diameter of substantially 150 mm. Moreover, the
probe assembly
100 beneficially has a longitudinal length "L", disregarding attachment of the
cladding 200
and its associated communication link 120, in a range of 0.5 metres to 5
metres, more
beneficially in a range of 1 metre to 3 metres and beneficially substantially
1.5 metres.
The system 300 is capable of being adapted to perform one or more of the
following
functions:
(a) Well leak detection, wherein the system 300 is operable to function as a
Well Leak
Detector (WLD). Leak depth accuracy to within an order of a centimetre is
feasible.
Moreover, leak rates in a range of 0.02 litres/minute to 300 litres/minute are
susceptible to being detected and monitored by using the system 300; leak
detection
in production packers, expansion joints, tubing, down-borehole 10 safety
valves, one
or more casings in a well associated with the borehole 10, and in a wellhead
associated with the borehole 10 are susceptible to being monitored using the
system
300; in operation, it is often not necessary when using the system 300 in the
borehole
10 to pull drill-string tubing up for identifying and monitoring a failing
barrier in a well;
(b) Well sand detection, wherein the system 300 is operable to function as a
Well Sand
Detector (WSD). Sand is probably a biggest challenge to operators in the oil
industry.
Sand fills up the borehole 10 and chokes back productivity of the borehole 10
when
used for oil extraction. Sand erodes well equipment and facilities, causing
breakdown
and sometimes causing blowouts. The system 300 is susceptible to being used to
identify sand-producing regions of geological strata, namely sand-producing
intervals,
and is also susceptible to being used to identify failures in sand control
devices
employed in conjunction with sand control for the borehole 10 when used to
extract
oil. Beneficially, the probe assembly 100 is implemented such that its housing
has a
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relatively smaller diameter, for example in a range of 40 mm to 80 mm, when
adapted
specifically for well sand detection. Acoustic energy is generated in the
housing
when sand particles impact upon the casing when the probe assembly 100 is in
use,
wherein the acoustic energy has a characteristic frequency spectrum by which
the
sand can be identified; at least a portion of the transducer array 320 is then
specifically adapted for sensing such acoustic radiation resulting from sand
impact on
the probe assembly 100;
(c) Well flow detection, wherein the system 300 is operable to function as a
Well Flow
Detector (WFD); the system 300 configured to function as a well flow detector
is
susceptible in operation to providing detailed information about an inflow
profile from
the borehole 10 when used for oil extraction, for example for providing
relative
velocity profiles between different producing or injecting intervals of the
borehole 10,
for example those intervals which are not contributing at all to oil
extraction; and
(d) Well annular flow detection, wherein the system 300 is operable to
function as a Well
Annular Flow monitor (WAF); the system 300 operable as the Well Annular Flow
monitor is capable of detecting and locating flow behind a pipe in an annulus
between
a liner tube, namely casing, and a geological formation; the system 300 is
thereby
operable to detect contamination of groundwater, one or more underground
blowouts,
sustaining liner tube pressure, one or more undesirable water cuts, and one or
more
undesirable gas cuts when drilling the borehole 10.
The system 300 is optionally optimized to perform one of functions (a) to (d).
Alternatively,
the system 300 can be optimally designed to perform several of these functions
and to
dynamically switch between such functions when in use. Certain of the
functions (a) to (d)
are serviced in the aforementioned first passive mode, whereas other of the
functions (a) to
(d) are addressed by the system 300 operating in its second active mode. In
general, a cost
and complexity of the system 300 increases as it is required to be more
versatile in
dynamically performing diverse functions.
Expressions such as "including", "comprising", "incorporating", "consisting
of', "have", "is"
used to describe and claim the present invention are intended to be construed
in a non-
exclusive manner, namely allowing for items, components or elements not
explicitly
described also to be present. Reference to the singular is also to be
construed to relate to
the plural.
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Numerals included within parentheses in the accompanying claims are intended
to assist
understanding of the claims and should not be construed in any way to limit
subject matter
claimed by these claims.
